soft starter

Difference between DOL, Star Delta, VFD and Soft starter

DOL-Direct on line Starter: here the starting current will be 6 times of full load current. A bimetallic thermal overload relay provides protection against the over load. There will be no reduction of starting torque during starting. Star Delta Starter: In order to limit the starting current of motors this method is followed. Initially motor…

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How to calculate cable size for LT Motors

What is the difference between LT and HT Motors? Well, as the word LT (Low Tension i.e. Low Voltage) and HT (High Tension i.e. High Voltage) or low torque and high torque respectively describe the whole story itself. its also depends on the availability of supply voltage, i.e. in USA and EU, LT Motors ranges…

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numerical relay

Why Numerical Relay over Electromechanical Relay

Advantages of Numerical relays 1.      Compact Size Electromechanical Relay makes use of mechanical comparison devices, which cause the main reason for the bulky size of relays. It uses a flag system for the indication purpose whether the relay has been activated or not. While numerical relay is in compact size and use indication on LCD…

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generator troubleshooting

Troubleshooting guide for generator

Brief introduction The following problems listed below are provided the following: Known problems Possible causes of the known problems Repair to correct the known problems Fault diagnosis   1). When the starting switch is in the (ON) position, the engine crankshaft does not rotate. Possible causes: 1. Low battery output voltage Check the battery status…

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maintenance of transformer

Maintenance of Transformer

A power transformer is most costly and essential equipment of an electrical transformer. So for getting high performance and long functional life of the transformer, it is desired to perform various maintenance activities. Not only that, a power transformer also requires various maintenance actions including measurement and testing of different parameters of the transformer. There…

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vector group test of transformer

Vector Group Test of Power Transformer

Vector Group Test of Transformer The vector group of transformer is an essential property for successful parallel operation of transformers. Hence every electrical power transformer must undergo through vector group test of transformer at factory site for ensuring the customer specified vector group of transformer. The phase sequence or the order in which the phases…

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transformer routine testing

Type Test and Routine Test of Transformer

For confirming the specifications and performances of an electrical power transformer it has to go through numbers of testing procedures. Some tests are done at manufacturer premises before delivering the transformer. Mainly two types of transformer testing are done at manufacturer premises- type test of transformer and routine test of transformer. In addition to that…

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What is Motor soft starter

Motor soft starter A motor soft starter is a device used with AC electrical motors to temporarily reduce the load and torque in the power train and electric current surge of the motor during start-up. This reduces the mechanical stress on the motor and shaft, as well as the electrodynamic stresses on the attached power…

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restricted earth fault

Restricted Earth Fault Protection of Transformer | REF Protection

REF Protection: An external fault in the star side will result in current flowing in the line current transformer of the affected phase and at the same time a balancing current flows in the neutral current transformer, hence the resultant current in the relay is therefore zero. So this REF relay will not be actuated…

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air core transformer

Air Core Transformer

If an alternating current is supplied to a coil, an alternating magnetic field is produced surrounding it. If another coil is brought inside this magnetic field, an alternating emf is induced across the second coil also as per Faraday’s law of electromagnetic induction. This induced emf in the second coil can be utilized to feed…

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